/Engine/Source/Runtime/Slate/Public/Widgets/Layout/SWidgetSwitcher.h
Removes a slot with the corresponding widget in it. Returns the index where the widget was found, otherwise -1.
int32 RemoveSlot ( [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SWidget](API\Runtime\SlateCore\Widgets\SWidget) > WidgetToRemove )